Supermarket giant Tesco has been caught up in a new row over sustainable tuna after it emerged it was stocking a cut-price brand which campaigners claimed harmed other wildlife

Greenpeace said that after pledging to make sure all its own brand tuna was sustainably caught in 2012, Tesco had started to stock "Oriental & Pacific" tinned tuna which the green group claimed was "dirty" because it is caught in a way that can kill sharks, rays and turtles.

Tesco was ranked in a "must try harder" category of a tuna league table drawn up by Greenpeace over the action the company is taking to make sure tinned tuna is sustainably caught.

But Tesco said it had moved much faster than many competitors to make sure its own-brand tuna was 100% caught using a pole and line, which avoids catching other species by accident.

And it had promised to use sustainable tuna in other products which use tuna, such as sandwiches and salads, the UK's biggest supermarket said, and will shortly issue a timetable for completing the move.

Sainsbury's was praised by Greenpeace as being at the forefront of sustainable tuna, with three-quarters of all tinned tuna sold by the retailer classed as sustainable.

Waitrose, the Co-operative, Marks & Spencer and Morrisons were also classed as market leaders.

Morrisons was given a 100% improved award for increasing the amount of its own-brand tuna being caught sustainably from 50% in the last league table in 2011 to 100% in 2014.

Campaigner and celebrity chef Hugh Fearnley-Whittingstall, who is featuring the issue on his Fish Fight programme on Channel 4 tonight said: "The Fish Fight and Greenpeace tuna campaign has been a huge success - our supermarkets and big tuna brands all told us they didn't want their names on unsustainable tuna, but a number of them are finding new ways to keep 'dirty' tuna on the shelves.

"Tesco made one of the biggest commitments of all to sell the most sustainable tuna, but as our new Fish Fight programme shows, they now stock a new brand called Oriental & Pacific, which is caught using methods that accidentally catch and kill endangered animals like turtles, rays and sharks.

"There's no information on Oriental & Pacific tins to tell shoppers how the tuna was caught.

"If they really care about our oceans then Tesco should take this tuna off the shelves today."

Ariana Densham, Greenpeace UK oceans campaigner, added: "Morrisons joins Sainsbury's as a market leader on tuna sustainability. They have eliminated unsustainable tuna from their products, which is great news for sharks, turtles and rays.

"If Tesco wants to catch up with the front runners and win back consumer confidence, they must take this dirty tuna off their shelves today."

A Tesco spokesman said: "The Greenpeace assessment is simply wrong.

"We moved much faster than many of our competitors to make sure our own-brand tuna is 100% pole and line. We have also promised to use sustainable tuna in other products like pastas, sandwiches and salads.

"Many of our competitors continue to sell non-pole and line caught tuna. Customers have a great choice of sustainable tuna at Tesco."

Greenpeace said that tuna in the Oriental & Pacific brand was "dirty" because it was caught in big nets known as purse seines, using "fish aggregation devices" or floating rafts which attracted not just tuna but other species that are then accidentally caught in the nets.

LDH, the company which owns the Oriental & Pacific (O&P) tuna brand, said it "totally refutes" any claim it was dirty, which implied there was something wrong with the product itself or that the skipjack tuna in it was unsustainably caught.

In a statement the company, which supplies products such as canned tomato products, fish, fruit and vegetables and dried pasta, said: "At least 85% of the tuna we sell is fished using the pole and line method; our O&P brand skipjack tuna is caught using the purse seine fishing method, which accounts for 63% of all tuna caught around the globe.

"Credible scientific research by the Regional Fisheries Management Organisations shows that stocks of skipjack tuna are healthy.

"All of our tuna suppliers are members of the International Seafood Sustainability Foundation and support its research-led initiatives for long-term conservation of tuna stocks, reducing by-catch and promoting eco-system health.

"We are fully committed to supporting our supply base in these on-going efforts and their work to support the scientific community in order to achieve best practice."